The present invention relates to holographic printers. According to a preferred embodiment a method and apparatus for recording and printing holographic stereograms from digital data is disclosed.
For over 50 years holograms have been produced by the general technique of illuminating an object with coherent light and arranging that the scattered light falls onto a photosensitive recording material that is also illuminated by a mutually coherent reference beam (see for instance E. N. Leith et al., “Reconstructed Wavefronts and Communication Theory”, Journal of the Optical Society of America 53, 1377-81 1963). However, with such a technique one requires a physical object in order to make an holographic representation of this object and usually the size of the holographic image corresponds in a 1:1 fashion with the size of the object holographed. For many practical applications this technique is hence unsuitable.
An alternative technique of generating and then directly writing the fundamental interference pattern that characterizes an hologram has been discussed and investigated (see for instance U.S. Pat. No. 4,701,006). However, even with today's computer resources, calculation of the interference pattern by Fourier transforms remains a daunting computational task for larger holograms. In addition it is still highly difficult and costly to write such patterns once calculated, the preferred technique being by electron beam.